
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
		<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
		<title>用键盘控制DIV</title>
		<style type="text/css">
			html,body{overflow:hidden;}
			body{margin:0;padding:0;}
			pre{color:green;padding:10px 15px;background:#f0f0f0;border:1px dotted #333;font:12px/1.5 Courier New;margin:12px;}
			span{color:#999;}
			#box{position:absolute;top:50px;left:300px;width:100px;height:100px;background:red;}
		</style>
		<script type="text/javascript">
			window.onload = function ()
			{
				var oBox = document.getElementById("box");
				var bLeft = bTop = bRight = bBottom = bCtrlKey = false;
				
				setInterval(function ()
				{
					if (bLeft)
					{
						oBox.style.left = oBox.offsetLeft - 10 + "px"
					}
					else if (bRight)
					{
						oBox.style.left = oBox.offsetLeft + 10 + "px"
					}
					
					if (bTop)
					{
						oBox.style.top = oBox.offsetTop - 10 + "px"	
					}
					else if(bBottom)
					{
						oBox.style.top = oBox.offsetTop + 10 + "px"
					}
					//防止溢出
					limit();
				},30);	
				
				document.onkeydown = function (event)
				{
					var event = event || window.event;
					bCtrlKey = event.ctrlKey;
					
					switch (event.keyCode)
					{
						case 37:
							bLeft = true;
							break;
						case 38:
							if(bCtrlKey)
							{
								var oldWidth = oBox.offsetWidth;
								var oldHeight = oBox.offsetHeight;
								
								oBox.style.width = oBox.offsetWidth * 1.5 + "px";
								oBox.style.height = oBox.offsetHeight * 1.5 + "px";				
								
								oBox.style.left = oBox.offsetLeft - (oBox.offsetWidth - oldWidth) / 2 + "px";
								oBox.style.top = oBox.offsetTop - (oBox.offsetHeight - oldHeight) / 2 + "px";
								
								break;	
							}
							bTop = true;
							break;
						case 39:
							bRight = true;
							break;
						case 40:
							if(bCtrlKey)
							{
								var oldWidth = oBox.offsetWidth;
								var oldHeight = oBox.offsetHeight;
								
								oBox.style.width = oBox.offsetWidth * 0.75 + "px";
								oBox.style.height = oBox.offsetHeight * 0.75 + "px";				
								
								oBox.style.left = oBox.offsetLeft - (oBox.offsetWidth - oldWidth) / 2 + "px";
								oBox.style.top = oBox.offsetTop - (oBox.offsetHeight - oldHeight) / 2 + "px";
								
								break;	
							}
							bBottom = true;
							break;
						case 49:
							bCtrlKey && (oBox.style.background = "green");
							break;
						case 50:
							bCtrlKey && (oBox.style.background = "yellow");
							break;
						case 51:
							bCtrlKey && (oBox.style.background = "blue");
							break;
					}
					
					return false
				};
			
				document.onkeyup = function (event)
				{
					switch ((event || window.event).keyCode)
					{
						case 37:
							bLeft = false;
							break;
						case 38:
							bTop = false;
							break;
						case 39:
							bRight = false;
							break;
						case 40:
							bBottom = false;
							break;
					}
				};
			
				//防止溢出
				function limit()
				{
					var doc = [document.documentElement.clientWidth, document.documentElement.clientHeight]
					//防止左侧溢出
					oBox.offsetLeft <=0 && (oBox.style.left = 0);
					//防止顶部溢出
					oBox.offsetTop <=0 && (oBox.style.top = 0);
					//防止右侧溢出
					doc[0] - oBox.offsetLeft - oBox.offsetWidth <= 0 && (oBox.style.left = doc[0] - oBox.offsetWidth + "px");
					//防止底部溢出
					doc[1] - oBox.offsetTop - oBox.offsetHeight <= 0 && (oBox.style.top = doc[1] - oBox.offsetHeight + "px")
				}
			};
		</script>
	</head>
	<body>
		<pre>
		红色方块为键盘操作区域，您可以进行如下操作：
		
		上：↑ 下：↓ 左：← 右：→
		
		Ctrl + 1 : 背景变为绿色
		Ctrl + 2 : 背景变为黄色
		Ctrl + 3 : 背景变为蓝色
		Ctrl + ↑ : 放大
		Ctrl + ↓ : 缩小
		</pre>
		<div id="box"></div>
	</body>
</html>
